The satisfactory removal of soils/stains is a particular challenge to the formulator of a detergent composition for use in laundry and dishwashing machines.
Traditionally, the removal of soils/stains has been facilitated by the use of surfactants. Of these, anionic surfactants have been found to give the most effective cleaning performance, especially at high levels.
Additional cleaning benefits may also be seen with the use of enzymes, for example, in the removal of proteinaceous stains/soils such as blood, egg, chocolate, gravy and the like.
A problem encountered with the use of enzymes as components of detergents is that enzyme activity in the wash may be reduced by the presence of other detergent components in the wash solution such as high levels of anionic surfactants.
One solution to this problem would be to reduce the level of anionic surfactant present in the detergent composition. However, whilst this would ameliorate the problem, this is accompanied by a marked negative effect on the overall stain/soil removal performance. To overcome this problem, combinations of surfactants, such as anionic, nonionic and cationic surfactants have been used.
GB-1,375,450 discloses a detergent composition which is asserted to provide effective cleaning and soil removal performance. The composition comprises an anionic surfactant, a cationic surfactant together with a proteolytic enzyme, wherein said cationic surfactant comprises two hydrophobic long chains. Specifically disclosed as suitable cationic surfactants are alkyl quaternary ammonium species as well as the ester compound formed from two moles of stearic acid and one mole of triethanol-methyl-ammonium chloride, e.g. N,N-di(2-stearoyloxyethyl)-N-(2-hydroxyethyl)-N-methyl ammonium chloride. However, a problem encountered with such cationic surfactants is their relative insolubility in the wash which diminishes their value in detergent compositions.
EP-B-8142 discloses liquid detergent compositions comprising a ternary surfactant system containing anionic, nonionic and cationic surfactants. More particularly disclosed is a liquid composition comprising 24% of an anionic surfactant (LAS), 18.5% of a nonionic surfactant (C.sub.45 E7) and 3.5% of Coconut (C.sub.12 -C.sub.14) dihydroxyethylmethyl ammonium chloride together with 0.4% of a Maxatase proteolylic enzyme, and wherein said composition is asserted to provide good soil removal performance.
EP-B-51986 discloses a granular laundry detergent composition which is asserted to provide good grease and oil removal performance together with clay soil detergency. The composition comprises, as a surfactant system a specified mixture of anionic, nonionic and water-soluble C.sub.10 -C.sub.14 alkyl trimethyl quaternary ammonium cationic surfactant, wherein said cationic surfactant is in amount from 0.2% to 2% by weight. The composition may additionally comprise a proteolytic enzyme.
Another potential solution to these problems would be to use detergent particles with different solubility rates. However, this would greatly increase the cost of the manufacturing process. An exemplary disclosure is given in EP-A-0,342,043 where the anionic surfactant and the enzyme are in two different particulate multi ingredient components. The particulate containing the enzyme has a solubility rate superior to the surfactant particulate and this superior solubility rate may be provided by a cationic surfactant.
Notwithstanding the advances in the art represented by the above disclosures, there is still a need for detergent compositions which provide effective soil/stain removal performance, which avoid degradation of the detergent components and which are not detrimental to the environment.
The Applicant has now surprisingly found that the provision of a cationic ester surfactant ameliorates these problems. Not to be bound by theory, it is believed that such component reduces the critical micelle concentration of any anionic surfactant present in the composition. Hence, reducing the concentration of anionic surfactant monomers in the wash improves the enzyme performance. Further enhanced soil removal benefits are observed where the cationic ester surfactant contains one hydrophobic chain.
The Applicant has also found that where a detergent composition contains a surfactant system comprising an anionic surfactant and a cationic ester surfactant, in combination with a proteolytic enzyme enhanced stain/soil removal is obtained, especially on proteinaceous stains.
The Applicant has found that the further addition of an amylolytic enzyme to the composition of the present invention enhances the overall soil/stain removal performance.
It is therefore an object of the present invention to provide compositions suitable for use in laundry and machine dishwashing methods producing enhanced stain removal.